Structure-Activity Relationship of Membrane-Targeting Cationic Ligands on a Silver Nanoparticle Surface in an Antibiotic-Resistant Antibacterial and Antibiofilm Activity Assay

Light-Activable Silver Nanoparticles for Combatting Antibiotic-Resistant Bacteria and Biofilms

Silver nanoparticles (AgNPs) are among the most widely used nanoparticulate materials for antimicrobial applications. The innate antibacterial properties of AgNPs are closely associated with the release of silver ions (Ag+) and the generation of reactive oxygen species (ROS). Multiple reports have elaborated on the synergistic effect against bacteria by combining photosensitizers with AgNPs (PS-AgNPs). This combination allows for the light-activated generation of Ag+ and ROS from PS-AgNPs. This is an efficient and controlled approach for the effective elimination of pathogens and associated biofilms. This review summarizes the design and synthetic strategies to produce PS-AgNPs reported in the literature. First, we explore multiple bacterial cell death mechanisms associated with AgNPs and possible pathways for resistance against AgNPs and Ag+. The next sections summarize the recent findings on the design and application of PS-AgNPs for the inactivation of resistant and non-resistant bacterial strains as well as the elimination and inhibition of biofilms. Finally, the review describes major outcomes in the field and provides a perspective on the future applications of this burgeoning area of research.

The Substantial Role of Cell and Nanoparticle Surface Properties in the Antibacterial Potential of Spherical Silver Nanoparticles

Purpose

Although it is well known that the size, shape, and surface chemistry affect the biological potential of silver nanoparticles (AgNPs), the published studies that have considered the influence of AgNP surface on antibacterial activity have not provided conclusive results. This is the first study whose objective was to determine the significance of the surface net charge of AgNPs on their antibacterial potential, attraction to bacterial cells, and cell envelope disruption, considering differences in bacterial surface properties.

Methods

We evaluated five commercial AgNP colloids with identical size and shape but different surface ligands. We thoroughly characterized their physicochemical properties, including the zeta potential, hydrodynamic diameter, and polydispersity index, and determined the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), along with silver absorption into bacterial cells. Moreover, we investigated structural changes in bacteria treated with AgNPs by using a crystal violet assay and electron microscopy.

Results

The zeta potential of AgNPs ranged from -47.6 to +68.5 mV, with a hydrodynamic diameter of 29-87 nm and a polydispersity index of 0.349-0.863. Bacterial susceptibility varied significantly (0.5 ≤ MIC ≤ 256 µg Ag/mL; 1 ≤ MBC ≤ 256 µg Ag/mL); we found the lowest susceptibility in bacteria with a cell wall or a polysaccharide capsule. The most active AgNPs (0.5 ≤ MIC ≤ 32 µg Ag/mL; 2 ≤ MBC ≤ 64 µg Ag/mL) had a moderate surface charge (-21.5 and +14.9 mV). The antibacterial potential was unrelated to ion dissolution or cell envelope disruption, and bacterial cells absorbed less of the most active AgNPs (1.75-7.65%).

Conclusion

Contrary to previous reports, we found that a moderate surface charge is crucial for the antibacterial activity of AgNPs, and that a significant attraction of the nanoparticle to the cell surface reduces the antibacterial potential of AgNPs. These findings challenge the existing views on AgNP antibacterial mechanisms and interactions with bacterial cells.

Structural Engineering of Cationic Block Copolymer Architectures for Selective Breaching of Prokaryotic and Eukaryotic Biological Species

Positively charged antimicrobial polymers are known to cause severe damage to biological systems, and thus synthetic strategies are urgently required to design next-generation nontoxic cationic macromolecular architectures for healthcare applications. Here, we report a structural-engineering strategy to build cationic linear and star-block copolymer nanoarchitectures having identical chemical composition, molar mass, nanoparticle size, and positive surface charge, yet they differ distinctly in their biological action in breaching prokaryotic species such as E. coli (Gram-negative bacteria) without affecting eukaryotic species like red-blood and mammalian cells. For this purpose, linear and star-block structures are built on a polycaprolactone biodegradable platform having an imidazolium positive handle. Under physiological conditions, the linear architecture exhibits toxicity indiscriminately to all biological species, whereas its star counterpart is remarkably selective in membrane breaching action toward bacteria while maintaining inertness toward eukaryotic species. Confocal microscopy analysis of HPTS fluorescent dye-loaded star-polymer nanoparticles substantiated their antimicrobial action in E. coli. Tissue-penetrable near-infrared fluorescent dye (IR-780) loaded NP aided the in vivo biodistribution analysis and ex vivo quantification of cationic species' accumulations in vital organs in mice. Azithromycin, a clinical water-insoluble macrolide, is delivered from the star platform to accomplish synergistic antimicrobial activity by the combination of bactericidal-bacteriostatic action of the polymer carrier and drug together in a single system.

Membrane-anchoring selenophene viologens for antibacterial photodynamic therapy against periodontitis via restoring subgingival flora and alleviating inflammation

Antibacterial photodynamic therapy (aPDT) has emerged as a promising strategy for treating periodontitis. However, the weak binding of most photosensitizers to bacteria and the hypoxic environment of periodontal pockets severely hamper the therapeutic efficacy. Herein, two novel oxygen-independent photosensitizers are developed by introducing selenophene into viologens and modifying with hexane chains (HASeV) or quaternary ammonium chains (QASeV), which improve the adsorption to bacteria through anchoring to the negatively charged cell membrane. Notably, QASeV binds only to the bacterial surface of Porphyromonas gingivalis and Fusobacterium nucleatum due to electrostatic binding, but HASeV can insert into their membrane by strong hydrophobic interactions. Therefore, HASeV exhibits superior antimicrobial activity and more pronounced plaque biofilm disruption than QASeV when combined with light irradiation (MVL-210 photoreactor, 350-600 nm, 50 mW/cm2), and a better effect on reducing the diversity and restoring the structure of subgingival flora in periodontitis rat model was found through 16S rRNA gene sequencing analysis. The histological and Micro-CT analyses reveal that HASeV-based aPDT has a better therapeutic effect in reducing periodontal tissue inflammation and alveolar bone resorption. This work provides a new strategy for the development of viologen-based photosensitizers, which may be a favorable candidate for the aPDT against periodontitis.

Regulating bacterial biofilms in food and biomedicine: unraveling mechanisms and Innovating strategies

Bacterial biofilm has brought a lot of intractable problems in food and biomedicine areas. Conventional biofilm control mainly focuses on inactivation and removal of biofilm. However, with robust construction and enhanced resistance, the established biofilm is extremely difficult to eradicate. According to the mechanism of biofilm development, biofilm formation can be modulated by intervening in the key factors and regulatory systems. Therefore, regulation of biofilm formation has been proposed as an alternative way for effective biofilm control. This review aims to provide insights into the regulation of biofilm formation in food and biomedicine. The underlying mechanisms for early-stage biofilm establishment are summarized based on the key factors and correlated regulatory networks. Recent developments and applications of novel regulatory strategies such as anti/pro-biofilm agents, nanomaterials, functionalized surface materials and physical strategies are also discussed. The current review indicates that these innovative methods have contributed to effective biofilm control in a smart, safe and eco-friendly way. However, standard methodology for regulating biofilm formation in practical use is still missing. As biofilm formation in real-world systems could be far more complicated, further studies and interdisciplinary collaboration are still needed for simulation and experiments in the industry and other open systems.

Multifunctional O-phenanthroline silver(I) complexes for antitumor activity against colorectal adenocarcinoma cells and antimicrobial properties by multiple mechanisms

A series of O-phenanthroline silver(I) complexes were synthesized and characterized by infrared (IR) spectroscopy, mass spectrometry (MS), ¹H nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray crystallography. The cytotoxicity of the silver(I) complex (P-131) was evaluated in the cancer cell lines HCT-116, HeLa, and MDA-MB-231 and the normal cell line LO2 via MTT assays. The 50% inhibition concentration (IC₅₀) of P-131 on HCT116 cell line is 0.86 ± 0.03 μM. It is far lower than the IC₅₀ value of cisplatin (9.08 ± 1.10 μM), the IC₅₀ value of normal cell LO2 (76.20 ± 0.48 μM) is much higher than that of cisplatin (3.99 ± 0.74 μM), indicating that its anticancer effect is stronger than that of cisplatin, and its biological safety is greater than that of cisplatin. Furthermore, anticancer mechanistic studies showed that P-131 inhibited cell proliferation by blocking DNA synthesis and acted temporally on the nucleus in dividing HCT-116 cells. Moreover, P-131 increased intracellular reactive oxygen species (ROS) levels in a dose-dependent manner. Notably, 10 mg/kg P-131 showed better antitumor effects than oxaliplatin in an HCT116 human colorectal xenograft mouse model without inducing toxicity. Moreover, the microdilution broth method was used to evaluate the antimicrobial properties of P-131 against Pseudomonas aeruginosa and Candida albicans. A biofilm eradication study was also performed using the crystal violet method and confocal laser scanning microscopy.

Self-Therapeutic Nanomaterials: Applications in Biology and Medicine

Over past decades, nanotechnology has contributed to the biomedical field in areas including detection, diagnosis, and drug delivery via opto-electronic properties or enhancement of biological effects. Though generally considered inert delivery vehicles, a plethora of past and present evidence demonstrates that nanomaterials also exude unique intrinsic biological activity based on composition, shape, and surface functionalization. These intrinsic biological activities, termed self-therapeutic properties, take several forms, including mediation of cell-cell interactions, modulation of interactions between biomolecules, catalytic amplification of biochemical reactions, and alteration of biological signal transduction events. Moreover, study of biomolecule-nanomaterial interactions offers a promising avenue for uncovering the molecular mechanisms of biology and the evolution of disease. In this review, we observe the historical development, synthesis, and characterization of self-therapeutic nanomaterials. Next, we discuss nanomaterial interactions with biological systems, starting with administration and concluding with elimination. Finally, we apply this materials perspective to advances in intrinsic nanotherapies across the biomedical field, from cancer therapy to treatment of microbial infections and tissue regeneration. We conclude with a description of self-therapeutic nanomaterials in clinical trials and share our perspective on the direction of the field in upcoming years.

Recent Advances in the Development of Lipid-, Metal-, Carbon-, and Polymer-Based Nanomaterials for Antibacterial Applications

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to discover potential new antibiotics. The use of nanotechnology, encompassing a broad range of organic and inorganic nanomaterials, offers promising solutions. Organic nanomaterials, including lipid-, polymer-, and carbon-based nanomaterials, have inherent antibacterial activity or can act as nanocarriers in delivering antibacterial agents. Nanocarriers, owing to the protection and enhanced bioavailability of the encapsulated drugs, have the ability to enable an increased concentration of a drug to be delivered to an infected site and reduce the associated toxicity elsewhere. On the other hand, inorganic metal-based nanomaterials exhibit multivalent antibacterial mechanisms that combat MDR bacteria effectively and reduce the occurrence of bacterial resistance. These nanomaterials have great potential for the prevention and treatment of MDR bacterial infection. Recent advances in the field of nanotechnology are enabling researchers to utilize nanomaterial building blocks in intriguing ways to create multi-functional nanocomposite materials. These nanocomposite materials, formed by lipid-, polymer-, carbon-, and metal-based nanomaterial building blocks, have opened a new avenue for researchers due to the unprecedented physiochemical properties and enhanced antibacterial activities being observed when compared to their mono-constituent parts. This review covers the latest advances of nanotechnologies used in the design and development of nano- and nanocomposite materials to fight MDR bacteria with different purposes. Our aim is to discuss and summarize these recently established nanomaterials and the respective nanocomposites, their current application, and challenges for use in applications treating MDR bacteria. In addition, we discuss the prospects for antimicrobial nanomaterials and look forward to further develop these materials, emphasizing their potential for clinical translation.

Supramolecular Adhesive Materials with Antimicrobial Activity for Emerging Biomedical Applications

Traditional adhesives or glues such as cyanoacrylates, fibrin glue, polyethylene glycol, and their derivatives have been widely used in biomedical fields. However, they still suffer from numerous limitations, including the mechanical mismatch with biological tissues, weak adhesion on wet surfaces, biological incompatibility, and incapability of integrating desired multifunction. In addition to adaptive mechanical and adhesion properties, adhesive biomaterials should be able to integrate multiple functions such as stimuli-responsiveness, control-releasing of small or macromolecular therapeutic molecules, hosting of various cells, and programmable degradation to fulfill the requirements in the specific biological systems. Therefore, rational molecular engineering and structural designs are required to facilitate the development of functional adhesive materials. This review summarizes and analyzes the current supramolecular design strategies of representative adhesive materials, serving as a general guide for researchers seeking to develop novel adhesive materials for biomedical applications.

Rational design of dual-functional surfaces on polypropylene with antifouling and antibacterial performances via a micropatterning strategy

The hydrophobicity and inertness of the polypropylene (PP) material surface usually lead to serious biofouling and bacterial infections, which hamper its potential application as a biomedical polymer. Many strategies have been developed to improve its antifouling or antibacterial properties, yet designing a surface to achieve both antifouling and antibacterial performances simultaneously remains a challenge. Herein, we construct a dual-function micropatterned PP surface with antifouling and antibacterial properties through plasma activation, photomask technology and ultraviolet light-induced graft polymerization. Based on the antifouling agent poly(2-methacryloyloxyethyl phosphate choline) (PMPC) and the antibacterial agent quaternized poly(N,N-dimethylamino)ethyl methacrylate (QPDMAEMA), two different micropatterning structures have been successfully prepared: PP-PMPC-QPDMAEMA in which QPDMAEMA is the micropattern and PMPC is the coating polymer, and PP-QPDMAEMA-PMPC in which PMPC is the micropattern and QPDMAEMA is the coating polymer. The composition, elemental distribution and surface morphology of PP-PMPC-QPDMAEMA and PP-QPDMAEMA-PMPC have been thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. Compared with pristine PP, the two types of micropatterned PP films exhibit good surface hydrophilicity as characterized by water contact angle measurements. The results of anti-protein adsorption, platelet adhesion and antibacterial evaluation showed that PP-PMPC-QPDMAEMA and PP-QPDMAEMA-PMPC had good anti-protein adsorption properties, especially for lysozyme (Lyz). They can effectively prevent platelet adhesion, and the anti-platelet adhesion performance of PP-QPDMAEMA-PMPC is slightly better than that of the PP-PMPC-QPDMAEMA sample. The sterilization rate of S. aureus and E. coli is as high as 95% for the two types of micropatterned PP films. Due to the rational design of micropatterns on the PP surface, the two classes of dual-functional PP materials realize both the resistance of protein and platelet adhesion, and the killing of bacteria at the same time. We anticipate that this work could provide a design strategy for the construction of multifunctional biomedical polymer materials.

Nanoarchitectonics for enhanced antibacterial activity with Lactobacillus buchneri S-layer proteins-coated silver nanoparticles

Various multi-drug-resistant microorganisms have appeared while a single antibacterial agent is increasingly no longer adequate for dealing with these resistant microorganisms. Herein, commercially purchased 50 nm-average-diameter silver nanoparticles (AgNPs) and Lactobacillus buchneri-isolated surface-layer proteins (SLPs) as a capping agent were used to fabricate a hybrid antibacterial agent (SLP-AgNPs) with enhanced antibacterial activity, and the possible synergistic antibacterial mechanism was explored. Characterization results revealed that SLP-AgNPs were uniformly surrounded by protein corona provided from SLP, and the formulations were mainly mediated by the electrostatic interactions and hydrogen bonding, which was evidenced by the results of Fourier transform infrared spectroscopy. According to the antibacterial tests, the minimum inhibitory concentration of SLP-AgNPs against Salmonella enterica (0.010 mg/mL) and Staphylococcus aureus (0.005 mg/mL) was 5-10 times lower than that of bare AgNPs, and while SLP-AgNPs showed a higher antibiofilm activity. Furthermore, bacterial cells exposed to SLP-AgNPs exhibited higher cell membrane permeability and stronger inhibition of respiratory-chain dehydrogenase activity, resulting in more severe cell death compared with bare AgNPs. The synergistic effect of SLP on AgNPs was probably carried out by enhanced function of adhesion to bacteria and antibacterial ability of SLP and SLP's supramolecular lattice structure on the sustained release of silver ion.

Antibacterial Polymers Based on Poly(2-hydroxyethyl methacrylate) and Thiazolium Groups with Hydrolytically Labile Linkages Leading to Inactive and Low Cytotoxic Compounds

Herein, we develop a well-defined antibacterial polymer based on poly(2-hydroxyethyl methacrylate) (PHEMA) and a derivative of vitamin B1, easily degradable into inactive and biocompatible compounds. Hence, thiazole moiety was attached to HEMA monomer through a carbonate pH-sensitive linkage and the resulting monomer was polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. N-alkylation reaction of the thiazole groups leads to cationic polymer with thiazolium groups. This polymer exhibits excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) with an MIC value of 78 µg mL-1, whereas its degradation product, thiazolium small molecule, was found to be inactive. Hemotoxicity studies confirm the negligible cytotoxicity of the degradation product in comparison with the original antibacterial polymer. The degradation of the polymer at physiological pH was found to be progressive and slow, thus the cationic polymer is expected to maintain its antibacterial characteristics at physiological conditions for a relative long period of time before its degradation. This degradation minimizes antimicrobial pollution in the environment and side effects in the body after eradicating bacterial infection.

Acid-Induced Self-Catalyzing Platform Based on Dextran-Coated Copper Peroxide Nanoaggregates for Biofilm Treatment

Nanoantibacterial agents based on catalytic activity were limited due to the low levels of endogenous H₂O₂ in the microenvironment of bacterial biofilms. However, the additional H₂O₂ will trigger more side effects to healthy surroundings, which is still a great challenge. Herein, we report an acid-induced self-catalyzing platform based on dextran-coated copper peroxide nanoaggregates (DCPNAs) for antibiofilm and local infection therapy applications. The dextran-functionalized DCPNAs were mediated and conveniently purified via a dextran and ethanol precipitation method, which can also cluster nanodots into nanoaggregates and show good penetrability as well as biocompatibility. Bacterial biofilms were inhibited and destroyed by the reactive oxygen species generated from the Fenton reaction between the Cu²⁺ and H₂O₂ released from DCPNAs in an acidic environment, which did not require additional H₂O₂. As expected, the DCPNAs exhibit low cytotoxicity and excellent acid-induced antibacterial and antibiofilm ability. Moreover, the DCPNAs realized great therapeutic outcomes in the application for in vivo wound healing. The overall excellent properties associated with the DCPNAs highlight that they could be considered as a kind of ideal antimicrobial agents for microbial biofilm infection treatment.

Synthetic Antimicrobial Polymers in Combination Therapy: Tackling Antibiotic Resistance

Antibiotic resistance is a critical global healthcare issue that urgently needs new effective solutions. While small molecule antibiotics have been safeguarding us for nearly a century since the discovery of penicillin by Alexander Fleming, the emergence of a new class of antimicrobials in the form of synthetic antimicrobial polymers, which was driven by the advances in controlled polymerization techniques and the desire to mimic naturally occurring antimicrobial peptides, could play a key role in fighting multidrug resistant bacteria in the near future. By harnessing the ability to control chemical and structural properties of polymers almost at will, synthetic antimicrobial polymers can be strategically utilized in combination therapy with various antimicrobial coagents in different formats to yield more potent (synergistic) outcomes. In this review, we present a short summary of the different combination therapies involving synthetic antimicrobial polymers, focusing on their combinations with nitric oxide, antibiotics, essential oils, and metal- and carbon-based inorganics.

Antimicrobial Synergy of Silver-Platinum Nanohybrids With Antibiotics

Various bacterial pathogens are responsible for nosocomial infections resulting in critical pathophysiological conditions, mortality, and morbidity. Most of the bacterial infections are associated with biofilm formation, which is resistant to the available antimicrobial drugs. As a result, novel bactericidal agents need to be fabricated, which can effectively combat the biofilm-associated bacterial infections. Herein, for the first time we report the antimicrobial and antibiofilm properties of silver-platinum nanohybrids (AgPtNHs), silver nanoparticles (AgNPs), and platinum nanoparticles (PtNPs) against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The AgPtNHs were synthesized by a green route using Dioscorea bulbifera tuber extract at 100°C for 5 h. The AgPtNHs ranged in size from 20 to 80 nm, with an average of ∼59 nm. AgNPs, PtNPs, and AgPtNHs showed a zeta potential of -14.46, -1.09, and -11.39 mV, respectively. High antimicrobial activity was observed against P. aeruginosa and S. aureus and AgPtNHs exhibited potent antimicrobial synergy in combination with antibiotics such as streptomycin, rifampicin, chloramphenicol, novobiocin, and ampicillin up to variable degrees. Interestingly, AgPtNHs could inhibit bacterial biofilm formation significantly. Hence, co-administration of AgPtNHs and antibiotics may serve as a powerful strategy to treat bacterial infections.

Self-Assemblies Based on Traditional Medicine Berberine and Cinnamic Acid for Adhesion-Induced Inhibition Multidrug-Resistant Staphylococcus aureus

S. aureus is resistant to various first-line antibiotics, and seeking multifarious strategies aimed at effective control of antibiotic-resistant behavior is urgently needed. Here, we report a two-component directed self-assembly mode: the phytochemicals berberine and cinnamic acid can directly self-assemble into nanoparticles (NPs) displaying good bacteriostastic activity. Compared with several first-line antibiotics, the obtained nanostructures have a better inhibitory effect on multidrug-resistant S. aureus (MRSA) and stronger ability for biofilm removal. These qualities are attributed to the fact that organic assemblies can first spontaneously adhere to the surface of the bacteria, infiltrate into the cell, and then lead to converging attack against MRSA; thereafter, multipath bactericidal mechanisms of NPs on MRSA are found by both transcriptomic analysis and quantitative Polymerase Chain Reaction analysis. Moreover, when combined with spectral data and single crystal X-ray diffraction, the NPs' self-assembly mechanism governed by hydrogen bonds and π-π stacking interactions is clearly elucidated. These non-covalent interactions induce the NPs' formation of butterfly-like one-dimensional self-assembled units and finally layered three-dimensional spatial configuration. In addition, biocompatibility tests show that the NPs are nonhemolytic with little toxicity in vitro and in vivo. This directed self-assembly mode can offer a new perspective toward the design of biocompatible antimicrobial nanomedicines for clinical translation.

Host defense peptide mimicking poly-β-peptides with fast, potent and broad spectrum antibacterial activities

Microbial infections have always been serious challenges to human health considering that antibiotics almost inevitably induce microbial resistance. Therefore, it is urgent to develop a new antibacterial agent that is active against drug-resistant bacteria and is less susceptible to microbial resistance. In this work, a series of host defense peptide (HDP) mimicking antibacterial poly-β-peptides were synthesized, characterized and evaluated for their biological activities. The best poly-β-peptide within this study (20 : 80 Bu : DM) displays potent and broad spectrum antibacterial activity against antibiotic-resistant super bugs and low toxicity toward mammalian cells. Moreover, these poly-β-peptides are bactericidal and kill bacteria very fast within 5 min. An antimicrobial resistance test demonstrated that bacteria develop no resistance toward the selected poly-β-peptides even over 1000 generations. Our studies demonstrate that random copolymers of heterochiral poly-β-peptides, without the need for defined secondary structures, can mimic the antimicrobial HDP. These results imply the potential application of these poly-β-peptides as new antimicrobial agents to tackle drug resistant antimicrobial infections.

Fabrication of PMPC/PTM/PEGDA micropatterns onto polypropylene films behaving with dual functions of antifouling and antimicrobial activities

Polymer materials with high biocompatibility and versatile functions are urgently required in the biomedical field. The hydrophobic surface and inert traits of polymer materials usually encounter severe biofouling and bacterial infection which hinder the potential application of polymers as biomedical materials. Although many antifouling or antimicrobial coatings have been developed for modification of biomedical devices/implants, few can simultaneously fulfill the requirements for antimicrobial and antifouling activities. Herein, we constructed bifunctional micropatterns with antifouling and antimicrobial properties onto polypropylene (PP) films using argon plasma activation treatment, photomask technique and UV-initiated graft polymerization method. Different sizes of PMPC/PTM/PEGDA micropatterns were fabricated on PP films to yield patterned PP-PMPC/PTM/PEGDA as evidenced by infrared (IR) spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), where PMPC is poly(2-methacryloyloxyethyl phosphorylcholine) for enhancement of hydrophilicity and biocompatibility, PTM is poly(methacryloyloxyethyltrimethylammonium chloride) for contribution to antimicrobial activity and PEGDA is poly(ethylene glycol diacrylate) as the crosslinker. The surface hydrophilicity of patterned PP-PMPC/PTM/PEGDA was characterized by the static water contact angle test. The results showed that the PP sample with a micropattern with the size of 5 μm exhibited the best hydrophilicity. For biological assays of patterned PP-PMPC/PTM/PEGDA, the micropattern size at 5 μm performed the best for both antiplatelet adhesion and antimicrobial activities. We anticipate that this work could provide a new method for building bifunctional biomedical materials to promote the application of PP in biomedical fields.

Steric configuration-enabled selective antimicrobial activity of chiral cysteine

Antibiotics abusing caused multi-drug resistant bacteria was an urgent need to develop effective alternatives to antibiotics. L-Cysteine is an amino acid commonly found in organisms, which is usually used as food additive and detoxication, while the antibacterial activity of L-Cysteine against pathogenic bacteria is rarely reported. Here, we demonstrated the broad-spectrum and selected antibacterial properties of D-/L-Cysteine, for the first time, D-Cysteine (D-Cys) and L-Cysteine (L-Cys) exhibited distinct antibacterial activity based on different bacteria (Escherichia coli, Staphylococcus aureus, Listeria monocytogenes and Salmonella enteritis). Among the four bacteria, L-Cys exhibited preferred antibacterial activity against S. aureus, while D-Cys showed stronger antibacterial activity against other three bacteria compared with L-Cys. Through analyzing cell structure of E. coli, it was demonstrated that D/L-Cys could destroy the integrity of E. coli cell membrane, which further resulted in the leakage of cell contents and cell death. This work has a potential value for the development of chiral bacteriostatic materials.

Phthalocyanine functionalized poly(glycidyl methacrylate) nano-assemblies for photodynamic inactivation of bacteria

Self-assembled PGED-Pc nanoparticles are able to inactivate bacteria via the generation of reactive oxygen species in aqueous solution, while a facile immobilization strategy sheds light on the engineering of self-sterilizing surfaces to combat bacterial infections.

All-in-one NIR-activated nanoplatforms for enhanced bacterial biofilm eradication

The chronic infection of humans by antibiotic-resistant bacteria and their related biofilm have, so far, not been properly addressed. In the present work, we developed a novel antibacterial nanoplatform showing the most efficient antibiotic-resistant bacteria inhibition and biofilm eradication. This particular formulation contains tobramycin-conjugated graphene oxide, for efficiently capturing bacteria through electrostatic interactions and eliminating bacteria as a "nano-knife", and copper sulphide nanoparticles for enhancing the photothermal and photodynamic properties. This novel formulation can selectively eliminate bacteria over NIH 3T3 cells, and the biofilm eradication capacity was up to 70%. Importantly, the nanoplatforms can inhibit bacterial growth and promote the repair of antibiotic-resistant bacteria-infected wounds on rats without non-specific damage to normal tissue. This work provides an effective, simple, and rapid method for the design and fabrication of near-infrared light-induced nanoplatforms that offer possibilities to treat biofilm-related infections.

Novel wound dressing with chitosan gold nanoparticles capped with a small molecule for effective treatment of multiantibiotic-resistant bacterial infections

Wound infection caused by multiantibiotic-resistant bacteria has become a serious problem, and more effective antibacterial agents are required. Herein, we report the preparation of wound dressings using the biocompatible chitosan (CS) as a reducing and stabilizing agent in the synthesis of 2-mercapto-1-methylimidazole (MMT)-capped gold nanocomposites (CS-Au@MMT), with efficient antibacterial effects. The synergistic effects of AuNPs, MMT, and CS led to the disruption of bacterial membranes. After blending with gelatin, crosslinking with tannin acid, and freeze-drying, CS-gelatin (CS-Au@MMT/gelatin) dressing was prepared. It had good mechanical properties as well as efficient water absorption and retention capacities. It exhibited outstanding biocompatibility both in vitro and in a cell-based wound infection model. Moreover, the in vivo rabbit wound healing model revealed that the CS-Au@MMT/gelatin dressing possesses significant antibacterial potential against methicillin-resistant Staphylococcus aureus-associated wound infection. Therefore, the CS-Au@MMT/gelatin dressing described in this study may have huge potential in biomedical applications.

Silver bullets: A new lustre on an old antimicrobial agent

Silver was widely used in medicine to treat bacterial infections in the 19th and early 20th century, up until the discovery and development of the first modern antibiotics in the 1940s, which were markedly more effective. Since then, every new antibiotic introduced to the clinic has led to an associated development of drug resistance. Today, the threat of extensive bacterial resistance to antibiotics has reignited interest in alternative strategies to treat infectious diseases, with silver regaining well-deserved renewed attention. Silver ions are highly disruptive to bacterial integrity and biochemical function, with comparatively minimal toxicity to mammalian cells. This review focuses on the antimicrobial properties of silver and their use in synergistic combination therapy with traditional antibiotic drugs.

Thiazolium-derivative functionalized silver nanocomposites for suppressing bacterial resistance and eradicating biofilms

Commercial antibiotic therapies are becoming less efficient due to the emergence of bacterial resistance and the formation of bacterial biofilms.

Single Continuous Near-Infrared Laser-Triggered Photodynamic and Photothermal Ablation of Antibiotic-Resistant Bacteria Using Effective Targeted Copper Sulfide Nanoclusters

The emergence of antibiotic-resistant bacterial strains has made conventional antibiotic therapies less efficient. The development of a novel nanoantibiotic approach for efficiently ablating such bacterial infections is becoming crucial. Herein, a collection of poly(5-(2-ethyl acrylate)-4-methylthiazole-g-butyl)/copper sulfide nanoclusters (PATA-C4@CuS) was synthesized for efficient capture and effective ablation of levofloxacin-resistant Gram-negative and Gram-positive bacteria upon tissue-penetrable near-infrared (NIR) laser irradiation. In this work, we took advantage of the excellent photothermal and photodynamic properties of copper sulfide nanoparticles (CuSNPs) upon NIR laser irradiation and thiazole derivative as a membrane-targeting cationic ligand toward bacteria. The conjugated nanoclusters could anchor the bacteria to trigger the bacterial aggregation quickly and efficiently kill them. These conjugated nanoclusters could significantly inhibit levofloxacin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Bacillus amyloliquefaciens at 5.5 μg/mL under NIR laser irradiation (980 nm, 1.5 W cm^-2, 5 min), which suggested that the heat and reactive oxygen species (ROS) generated from the irradiated CuSNPs attached to bacteria were effective in eliminating and preventing the regrowth of the bacteria. Importantly, the conjugated nanoclusters could promote healing in bacteria-infected rat wounds without nonspecific damage to normal tissue. These findings highlight the promise of the highly versatile multifunctional nanoantibiotics in bacterial infection.